1. Field of the Invention
The present invention relates to the concurrent detection of the electrical and mechanical activity of the heart by non-invasive means, the processing of the data and its presentation to physicians and other health care providers with the objectives to diagnose a condition, monitor a condition, guide a therapeutic intervention, or provide prognosis regarding some pathology.
2. Description of the Prior Art
The heart is a complex pump that engineers may view as an electromechanical device. Its pumping performance varies from moment to moment or beat to beat as it reflects the dynamic and emotional state of the organism, a human or an animal, that it serves. The natural control of the heart is partly traced to the electrical activity of its tissues, which are partly influenced by the central nervous system, partly by chemical influences delivered through the blood, partly by the state of its own coronary circulation, as well as its past history, such as myocardial infarcts, occlusion of coronary arteries, trauma, and so on. The diagnosis and treatment of pathological heart function are dependent on measurements of these influences and on the hemodynamic performance of the pump.
The present invention in its preferred form relates to the concurrent detection of the electrical and mechanical activity of the heart by non-invasive means, the processing of the data and its presentation to physicians and other health care providers with the objectives to diagnose a condition, monitor a condition, guide a therapeutic intervention, or provide prognosis regarding some pathology. It could also be utilized to query information from other electrically active organs. This method is suitable for non-biological applications where electromagnetic radiation and physical position are to be sensed remotely from a source or multiple sources. This, for example could be accomplished with a plurality of the Laplacian sensors and the sonar of a submarine.
The performance of the human heart in health and disease has been quantitatively studied at least since William Harvey presented “De Motu Cordis” early in the 17th century. Non-invasive means for gathering such data regarding heart parameters have been used for more than a century. These means include auscultation, listening to the sounds from the chest with a stethoscope, recording roentgenograms and cine-radiograms (early 20th c.), electrocardiograms or ECGs (early 20th c.), pressure recordings, impedance cardiograms (Kubicek et al., mid-20th c.), electro-kymograms (cca. 1950), ballistocardiograms (cca. 1950), among others. Simultaneous access to localized electrical and mechanical activity has been elusive. ECGs provide considerable detail about the electrical activity of heart tissues, but very little about the heart's pumping. Body surface electrograms (BSE) and vectorcardiograms (VCG) showed great promise, but for various reasons have not become standard tools in cardiology. Ultrasonic techniques have emerged over the past two decades providing fine details about the architecture and dynamics of the heart, non-invasively. Various algorithms have evolved to quantify these aspects. Despite these advances, the simultaneous display and quantitative presentation of the electrical and mechanical activities have been inadequate, limited to a surface ECG recorded along with sophisticated ultrasonic studies, or, alternately, blood pressure monitoring during a sophisticated electrophysiologic study.
ECGs and BSEs are recorded according to certain conventions. A minimal ECG system comprises three electrodes on the body surface, two of which, the “active” electrodes, are connected to a differential amplifier and the third one serves as a potential reference, usually connected to ground. Ideally, the potential difference between the two active electrodes is amplified. The record is called bipolar when the active electrodes are far apart on the chest, for instance, placed on the left and right shoulders. The record is unipolar when there is one “active” electrode that is placed at one of many specific anatomic landmarks, the V-lead positions, near the heart, while the second electrode is not really active as it is the average of the potentials at three sites, the left and right arms and the left leg; this reference is called the Wilson terminal. This mode of recording is rather sensitive to the placement of the active electrode and allows identification of parts of the heart where the electrical activity is abnormal.
In BSE the number of active electrodes is large, usually ranging from 30 upward to more than 100; each one provides information about activity in its own vicinity. However, the signal is only moderately responsive to nearby electrical activity and it is often hard to distinguish local from more distant activity as the amplitude of the detected signal is proportional to the volume of contributing tissue mass and inversely proportional to its distance to the electrode.
Bipolar recordings with closely spaced electrodes are more sensitive to local activities but they are also selective with respect to the direction of travel of the electrical activity in the tissues. The electrical source of the signal travels inside the body and within the heart, and may be represented by an equivalent mobile dipole. When the line connecting the surface electrodes coincides with the travelling direction of the source, then the signal is strongest, when those are perpendicular, the signal vanishes. For this and other reasons, concentric electrodes have been used at least since 1950, when Fattorusso et al. reported that supplementary information may be extracted with such electrodes.